This invention relates generally to surgical apparatus and more particularly to bone screws for the retention of tissue grafts and bone plates.
Presently, a variety of bone screws and surgical procedures are used for the retention of craniomaxillofacial tissue grafts and bone plates with a primary objective being to minimize the surgical steps and to maximize fixation. These procedures generally fall into one of two categories: a self-threading screw that incorporates a self-cutting flute to minimize the need to surgically prepare a pilot hole or a self-threading screw without a self-starting cutting flute which always requires a surgically prepared pilot hole.
For the latter type, the physician must perform multiple operations which involves first locating and drilling a pre-sized hole. Once the pilot hole is prepared, the physician must relocate the hole to insert the self-threading bone screw. Since most of the craniomaxillofacial procedures require small diameter bone screws, relocating the pilot hole prior to insertion of the bone screw can be difficult. However, the advantage to this procedure, if performed correctly, is that the pre-drilled pilot hole will act as a guide to insert the self-threading bone screw and minimize the risk of screw and/or bone fractures due to excessive applied seating torque.
To overcome the surgical requirements of drilling a pilot hole into a surgical site prior to inserting a bone screw, a variety of bone screw systems have incorporated a self-starting cutting flute into the apex of the screw. This self-starting cutting flute is designed to initially penetrate and cut into the bone site and then to lead the self-threading features of the screw into place. Although, conceptually, these screws eliminate the pitfalls of a pre-drilled hole and maximize the bone screw fixation, locating and inserting these screws become difficult. Since a pilot hole is not drilled, these screws are difficult to locate and start in the denser cortical bone and effectively become challenging to insert. In addition, these screws require substantially higher seating torque which lead to greater risk of screw or bone fracturing during insertion.
An object of the present invention is the provision of apparatus to overcome the above noted prior art limitations. Another object is the provision of apparatus for rigidly fixing craniomaxillofacial tissue grafts and bone plates in a single surgical procedure. These and other objects and features of the invention will be apparent from the following description taken with reference to the accompanying drawings.
Briefly stated, a bone screw made in accordance with the present invention incorporates a sharp piercing twist drill point tip in series with a self-tapping threaded body. A cylindrical dome shaped head is formed distal to the tip and body of the bone screw that drives the screw in or out of the surgical site using a unique spline driver tool. The invention solves the problems of locating and self-starting a self-tapping bone screw into place while minimizing the surgical steps and maximizing the fixation. This invention allows the physician to take advantage of a pre-drilled hole without compromising the surgical results common to the standard multiple step procedure. Finally, the component provides the physician with a cost effective, easy to use, functional equivalent to rigidly fix craniomaxillofacial tissue grafts and bone plates in a desired surgical site.